1. Field of Invention
The present invention relates to a dolly with adjustable wheel assembly, and more particularly to a dolly with adjustable wheel assembly which provides movement of the dolly along two perpendicular axes.
2. Description of Related Arts
Hand trucks, such as dollies and four-wheeled transportation boards, are commonly used for carrying and transporting a load, especially heavy and bulky load, from one place to another. One type of conventional dolly includes a frame for holding a load and two wheels for movement along the axis of the frame. When a user uses the dolly to transport a heavy load and has to make a turn, the whole dolly, which includes the frame and the wheels, has to be turned together. That is to say, the user has to hold and turn the dolly which carries the heavy load in order to make a turn.
There are some major drawbacks for this kind of conventional dolly. First, the user has to turn the heavy load on the dolly when making a turn and without any displacement and without making any progress of movement. Second, the heavy load may be dislodged from its original position and collapsed while making a turn. Third, when the load is bulky and the space is not sufficient for making a turn, a user has to unload and adjust the position of the heavy and bulky load manually and reposition the dolly with respect to the load. For example, a rectangular bulky load is carried with the dolly across a L-shaped corridor. When the user approaches the corner of the L-shaped corridor, he or she has to unload and reposition the bulky load at the corner, and then moves the dolly to fit the load in order to pass through the corner. The lack of any mechanism in the conventional dolly to facilitate movement in two perpendicular directions makes it really inconvenience and ineffective as a transportation tool. Since building structures, either residential or commercial, usually will not provide a huge corridor and cannot avoid having corner points in the building structures, the need of making a turn at the corner is real and the problem of failing to provide any mechanism to solve the problem is a vital drawback.
Another type of hand truck is a four-wheeled transportation board, which is very primitive in the sense that there is no mechanism to secure a load on the transportation board and no handle or navigation means for the user to hold and move the board around, or to stop the board. There is simply no control or handle arrangement for this kind of four-wheeled transportation board.